Orthopaedic implant-related infections are not only costly to healthcare systems, but affect patients the world over. Contributing significantly to these infections are bacteria residing in established biofilms of nature that contaminate open fracture sites either at the time of trauma or during subsequent surgery. In an attempt to fight and prevent these infections, directly and locally, antibiotic surface coatings of implants have been investigated. However, antibiotics continue to have significant limitations due to evolving antibiotic resistance by microorganisms, a lack of long-term elution properties from implant surfaces and, in many instances, a limited spectrum of activity against Gram-negative and Gram-positive bacteria. Thus, novel antimicrobial coatings need to be developed for orthopaedic implants. Herein, we propose to investigate a novel antimicrobial - cationic steroid antimicrobial-13 (CSA-13) - which has superior broad-spectrum activity against Gram-negative and Gram-positive bacteria. We intend to use CSA-13 as a surface coating on orthopaedic fixation plates to prevent infection. To promote a strong infection signal in our experimental design, established biofilms of Staphylococcus aureus will be grown on coupons from the CDC biofilm reactor system, the latter provides a means to create standardized biofilms. The coupons will be inserted into a notch in the fixation plate on its underside and as a unit, the fixation plate/coupon will be placed directly onto the surface of the tibia of sheep. The evaluation of two sets of variables; CSA-13-coated or uncoated and biofilm-treated or untreated implants will determine if this novel antimicrobial coatings has the potential to fight and possibly prevent orthopaedic, biofilm implant-related infections. Furthermore, a second phase of the study will use tritium as a radiolabel on CSA-13 to determine the local and systemic effects of CSA-13 on tissue. By scintillation counting and histological analysis, the effects of CSA-13 on tissue and fracture healing will be determined. Taken together, the proposed experiments are designed to analyze first, the ability of the novel CSA-13 antimicrobial to fight and prevent orthopaedic implant-related infection promoted by a common orthopaedic pathogen, S. aureus, in an established biofilm and second, to determine if CSA-13 has detrimental effects on host tissue and end organs. We hope, by these means, to improve the orthopaedic trauma care of both civilian and military trauma patients.